Cut the capillary coupling in half and file or grind the cut ends until the two halves slip easily over the conduit.
Cut a short length of the conduit such that, with the two halves of capillary coupling at each end of it, there is a small gap of exposed conduit between them.
Drill two holes in the center of the conduit on opposite sides.
Slip your Vcc and GND wires through these two holes and out the end of the conduit.
Solder the ends of these two wires to the inner edges of the capillary coupling halves - do so before slipping them over the electrical conduit otherwise you will burn/melt the plastic. I had to heat the capillary coup[ling halves in a gas flame since my soldering iron was not up to the task. I then waited for them to cool a bit until the solder was solid and then when I applied my soldering iron it was enough to then re-melt the solder.
You can bind the capillary coupling halves to the electrical conduit with a smear of liquid nails glue or what ever you have at hand.
Take one of the door knobs and drill out the central hub (where the supplied bolt screws in from the other side of the door) such that you can pass the two electrical wires right through the center of the door knob.
That central hub of the door knob fits tightly inside the electrical conduit and you will have two nice flanges to fix to other components of your project.
This description should be enough but if you require a photo of my device I will put one up.
For the other part of the electrical contact I am going to use a couple of these hooks:
with some metalic stand-offs from the local Jaycar.
The stand-offs slip over the ends of the hooks and then rotate freely similar to a ball bearing.
Some small pieces of shrink tube will prevent the stand-offs from moving to far an d the conductive grease will lubricate them.
I might see of I can mount these hooks on a bit of wood then and then attach this to the frame via two bolts at each end with a spring, e.g. from a click pen, over them.
But you may just want to use a couple of bits of bent copper wire or strips of copper sheet.
It was just a matter of wandering around Bunnings Warehouse trying to fit various pieces together until I found matches in size.
But if anyone can figure out how to make a smaller slip ring out of easy to get bits and pieces< I would be interested in reading about it.
I did try making a slip ring out of 15mm (or there abouts) dowel and 20mm hard copper plumbing pipe. But then you have to try a drill holes in the center of the ends of the dowel, and it is impossible to get the holes perfectly centered. And you have to cut longitudinal grooves in the dowel so that the wire from one slip ring can pass beneath the other slip ring - much easier with the hollow electrical conduit.
Dunno Jimbo.....that was the description of the door knob that Bunnings Warehouse uses.
I guess the 'square round' is another way of saying 'cylinderical' where the transition from the front surface of the knob to the side surface of the knob is at 90 degrees as in the corner of a square.
,
